A person who likes to back out in every transactions or promises.
Someone said to buy/trade items but pull out in the last minute.
"Ken said he is going to buy that game, but instead he backed out, what a backoutter!"
Dave: "I am going to buy that doll for a girl if you buy one too."
Me: "Sure I can do that."
Dave: "Wait, I am not going to buy it."
Me: "What a backoutter...."